According to Dell, Kaby Lake-G caters better to casual mainstream gamers while the Alienware brand will stick to hardcore gamers and enthusiasts with the familiar Intel H-series and Nvidia GTX GPUs. The Intel-AMD processors will instead be used for Dell's mainstream families like the XPS line to provide GTX 1050-level graphics.
https://www.notebookcheck.net/Alienware-has-no-current-plans-for-Kaby-Lake-G.301014.0.html
The Kaby Lake-G with the RX Vega M GH might be a good option for the Alienware 13 if it really is on par with the 1060.
Too bad only the GL version is in the XPS 9575, but it's better to have good thermals.